The present invention relates to high-sensitivity sensors for sensing various physiological phenomena, such as respiratory activity, cardiac activity, body movements, sleeping activity, etc. The invention is particularly useful in sensing snoring, and is therefore described below as one of the preferred embodiments in a method and apparatus for detecting snoring and for actuating a stimulus device to produce a feedback response tending to reduce or eliminate the snoring.
The preferred embodiments of the invention described below utilize the type of sensors described in International Patent Application No. PCT/IL2004/000138, filed Feb. 12, 2004, and U.S. Pat. No. 6,621,278, the contents of which are incorporated herein by reference. It will be appreciated, however, that while such sensors are preferred, other types of sensors may also be used as described more particularly below.
The above-cited International Patent Application and U.S. patent describe sensors for sensing, with extremely high sensitivity, various parameters having a known or determinable relationship with respect to the transit time of an energy wave (e.g., electromagnetic, acoustic) through a medium (solid, liquid or gas). Briefly, this is done by transmitting a cyclically-repeating energy wave through a transmission channel in the medium; continuously changing the frequency of the transmission according to changes in the sensed parameter while maintaining the number of waves in a loop including the transmission channel as a whole integer; and utilizing the changes in frequency in the transmission channel to provide a continuous indication of the sensed parameter. Thus, a change in the sensed parameter changes the transit distance and/or the transit velocity, and thereby the transit time, of the energy wave through the transmission channel.
The above-cited International Patent Application discloses a sensor construction in which the medium of the transmission channel between the transmitter and receiver is a body of a soft elastomeric material having high transmissivity and low attenuation properties with respect to the transmitted energy waves. Such sensors are particularly useful as mechanical vibration sensors, both the displacement type and the acceleration type, which are to be brought into contact with an object for sensing mechanical vibrations in the object.
As will be described below, the present invention provides novel constructions of such mechanical vibration sensors which make them particularly useful for monitoring various physiological phenomena, including vital signs, e.g. respiratory activity (breathing), cardiac activity (heartbeat), and body movements. Potential applications of the present invention include apnea monitors, elderly are monitors, asthma attack monitors, and sleep-condition monitors. Examples of the latter application include devices to actuate an alarm in case an alarm condition is detected, to detect sleep disorders, to control a wake-up alarm for comfortable awakening, and to reduce or eliminate snoring.
The invention is particularly useful for detecting sleep disorders and for controlling a wake-up alarm since it efficiently senses various body activities, such as respiration rate, pulse rate, and body motions helpful in identifying a sleep disorder or comfortable wake-up time, e.g., as described in U.S. Pat. Nos. 5,101,831, 6,752,766 and 6,856,829, the contents of which are incorporated herein by reference.
The invention is also especially useful to reduce or eliminate snoring. Thus, it is generally recognized that snoring not only unduly disturbs those in the immediate vicinity, but probably more important, may be an indication of a serious sleep disorder which can lead to strokes, heart diseases, hypertension, etc. Many sound-type sensors have been developed for this purpose, but such sensors are also sensitive to sounds other than snoring sounds, and are therefore generally subject to a relatively high rate of false alarms.